Hydraulic brake apparatus for a vehicle

ABSTRACT

The present invention is directed to a hydraulic brake apparatus for applying braking force to each wheel of a vehicle in response to depression of a brake pedal. A master piston is received in a cylinder body to define a pressure chamber ahead of the master piston and a power chamber behind it. An auxiliary pressure source is provided for pressurizing the brake fluid in a reservoir to discharge power pressure. A control piston is slidably disposed in the cylinder body ahead of the master piston to be movable in response to movement thereof, so that a regulator chamber is defined ahead of the control piston, and a rear end thereof is exposed to the pressure chamber. A first passage is adapted to communicate the auxiliary pressure source with the power chamber, and a second passage is adapted to communicate the power chamber with the reservoir through the regulator chamber. A pressure increase valve device is disposed in the first passage to open or close the first passage in response to movement of the control piston. And, a pressure decrease valve device is disposed in the second passage to open or close the second passage in response to movement of the control piston. Preferably, a one way valve is disposed in the first passage, and a pressure restriction device may be disposed in the second passage.

This application claims priority under 35 U.S.C. Sec. 119 to No.9-190404, No. 9-190627 and No. 9-190703 filed in Japan on Jun. 30, 1997,the entire contents of which are herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hydraulic brake apparatus forsupplying a hydraulic brake pressure to each wheel brake cylindermounted on each wheel of a vehicle, and more particularly to theapparatus which is provided with a hydraulic pressure boosting device.

2. Description of the Related Arts

As for hydraulic brake apparatuses, various types are known and alreadyon a market, including the apparatus of a type provided with a hydraulicpressure boosting device. For instance, the U.S. Pat. No. 3,928,970discloses a power-assisted master cylinder using a source of fluid underpressure, which includes a piston movable in a cylinder bore, a pressurespace ahead of the piston having an outlet for connection to a brakecircuit, a power chamber behind the piston having an inlet forconnection to the source of the fluid under pressure, and a controlvalve assembly for controlling the supply of fluid from the pressuresource to the power chamber. It was the object of that patent to providethe assembly in which a piston is pedal operated but which does notrequire a movable inlet or inlet seals which move under pressure. And,there is disclosed a master cylinder assembly which includes a firstpiston and a second piston, between which a first pressure space isdefined and connected to a hydraulic pressure circuit. Ahead of thesecond piston, a second pressure space is defined and connected to aspace behind the first piston. An inlet valve member is provided forintroducing the pressure discharged from the pressure source into thesecond pressure space, and an exhaust valve is provided forcommunicating the second pressure space with a reservoir, and thesevalve members are adapted to be actuated in response to movement of thesecond piston.

Also, the British Patent Application GB 2170874A discloses aservo-assisted master cylinder assembly for a vehicle hydraulic brakingsystem which has a master cylinder with primary and secondary pistonsoperative to pressurize primary and secondary pressure spaces forprimary and secondary brake circuits. A servo chamber is defined behindthe primary piston, and pressurization of the servo chamber from asource of pressure fluid is controlled by valve means which comprises aspool operated solely by pressure in the primary space and a bias forcefrom servo pressure and spring in a bias chamber. In the assemblydisclosed in the application, the spool is arranged on a different axisfrom that of the master cylinder, i.e., in parallel with it, orperpendicularly to it.

According to the assemblies disclosed in the U.S. Patent and BritishPatent Application as described above, it is so arranged that thepressurized fluid which was regulated by a valve device is supplied to apower chamber (or, servo chamber). And, with respect to the regulatingact done by the regulator, the valve device is adapted to control abalance between the regulated pressure and the master cylinder pressure,which are applied to the front and rear of a control piston,respectively. In operation, the hydraulic pressure of the pressurizedfluid supplied from the source thereof is rapidly transmitted to thecontrol piston, to make the pressure balance by repetition of increasingand decreasing the pressure of the fluid. Therefore, with thepressurized and regulated fluid supplied to the power chamber (servochamber), a necessary boosting operation can be made. However, when abrake pedal is operated rapidly under the circumstance of a relativelylow temperature for instance, the pressure decreasing operation might beinitiated without sufficient amount of brake fluid supplied to the powerchamber, so that sufficient boosting operation might not be made. In thecase where the diameter of a passage for supplying the fluid to thepower chamber is relatively small, or the length of the passage isrelatively long, a proper response for boosting the pressure can not beobtained, so that conditions for designing the assembly will be severe.

According to the above-described assemblies, the regulated pressuredischarged from the regulator is provided for various hydraulic brakepressure controls such as the anti-skid control. However, when theregulated pressure is provided for the hydraulic brake pressure control,the hydraulic pressure in the power chamber will be varied in responseto variation of the regulated pressure. Then, the depressing force ofthe brake pedal will be varied in response to variation of the hydraulicpressure in the power chamber, whereby the brake pedal feeling to thevehicle driver might be deteriorated.

Furthermore, in order to increase the braking force when a rapid brakingoperation is made in case of emergency for example, Japanese PatentLaid-open Publication No. 9-24818 proposes a vehicle braking controlapparatus, which includes a regulator for regulating power pressuredischarged from a power source and supplying regulated pressure to wheelbrake cylinders during a normal braking operation, and changeover meansfor communicating the pressure source directly with the wheel brakecylinders in case of an emergency braking operation. That publicationdiscloses the regulator using a spool valve, and discloses means forvarying an area for receiving the regulated pressure, so as to provide adesired characteristic of the regulated pressure to the master cylinderpressure. In practice, a resilient member such as rubber is placed aheadof the spool valve through an engaging member, to restrict the pressureapplied to the spool valve, in accordance with increase of the area ofthe resilient member contacting with the engaging member. Also, JapanesePatent Laid-open Publication No. 9-24819 discloses an apparatus providedwith an orifice for increasing the braking force in case of theemergency braking operation.

According to the above-described Japanese Patent Laid-open PublicationNos. 9-24818 and 9-24819, it is possible to increase the braking forcein case of the emergency braking operation. In a transitional period ofthat braking operation, however, the braking force to de added may notnecessarily be sufficient. Furthermore, when the brake pedal isreleased, the braking force will not be released immediately thereafter,so that the vehicle driver will be uncomfortable in his brakingoperation. In order to avoid this, it is necessary to provide a pressuresensor in the hydraulic pressure circuit to detect the release of thebrake pedal. However, a relatively large delay occurs until the pressuredecreasing operation will be initiated after the release of the brakepedal is detected. In stead of the expensive pressure sensor, it ispreferable to employ a stroke sensor for detecting a stroke of the brakepedal. According to the apparatus disclosed in the publicationsdescribed above, however, it is very difficult to detect the release ofthe brake pedal. The apparatus disclosed in the U.S. Pat. No. 3,928,970is not adapted to increase the braking force in case of the emergencybraking operation as described in the Japanese publications.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide ahydraulic brake apparatus for a vehicle having a hydraulic pressureboosting device, with a proper boosting operation ensured.

It is another object of the present invention to provide a hydraulicbrake apparatus for a vehicle having a hydraulic pressure boostingdevice, with little variation of hydraulic pressure in a power chambercaused during the boosting operation.

It is a further object of the present invention to provide a hydraulicbrake apparatus for a vehicle having a hydraulic pressure boostingdevice, wherein braking force can be increased immediately when anemergency braking operation is initiated, and the braking force can bereleased properly and immediately when the braking operation isterminated.

In accomplish the above and other objects, a hydraulic brake apparatusis provided for applying braking force to each wheel of a vehicle inresponse to depression of a manually operated braking member. Theapparatus includes a cylinder body mounted on the vehicle, a reservoirfor storing brake fluid, a master cylinder having a master pistonslidably received in the cylinder body to define a pressure chamberahead of the master piston and a power chamber behind the master piston,so that the brake fluid in the reservoir is fed into the pressurechamber, and the master piston is moved in response to operation of themanually operated braking member to discharge hydraulic brake pressurefrom the pressure chamber. An auxiliary pressure source is provided forpressurizing the brake fluid in the reservoir to discharge powerpressure of a predetermined value. A control piston is slidably disposedin the cylinder body ahead of the master piston to be movable inresponse to movement of the master piston, so that the control pistondefines ahead thereof a regulator chamber, and exposes a rear endthereof to the pressure chamber. A first passage is adapted tocommunicate the auxiliary pressure source with the power chamber, and asecond passage is adapted to communicate the power chamber with thereservoir through the regulator chamber. A pressure increase valvedevice is disposed in the first passage to open or close the firstpassage in response to movement of the control piston. And, a pressuredecrease valve device is disposed in the second passage to open or closethe second passage in response to movement of the control piston.

Preferably, a one way valve device is provided for allowing the brakefluid to flow from the pressure increase valve device to the powerchamber and preventing the reverse flow. Furthermore, a modulator may beconnected with one end of the one way valve device to be connected withthe pressure increase valve device, to supply the hydraulic brakepressure discharged from the pressure increase valve device into wheelbrake cylinders of the vehicle in accordance with the driving conditionsof the vehicle. The one way valve device may be formed by a check valvewhich is disposed in the first passage at a portion thereof opening tothe power chamber.

A pressure restriction device may be provided for restricting thehydraulic brake pressure fed from the power chamber into the regulatorchamber in response to operation of the manually operated brakingmember.

The pressure restriction device may include a valve device which isdisposed in the second passage to normal open the second passage, andclose the second passage when the manually operated braking member isoperated rapidly, and a pressure decreasing device which is disposed inparallel with the valve device to decrease the hydraulic brake pressurefed into the regulator chamber in accordance with a predeterminedcharacteristic. The valve device may include a rapid operation detectingdevice for detecting operation of the manually operated braking memberto output a cut-off signal when the manually operated braking member isoperated at a speed greater than a predetermined speed, and a normallyopen electromagnetic valve for closing the second passage when the rapidoperation detecting device outputs the cut-off signal.

A pressure control device may be disposed between the power chamber andthe regulator chamber to control the pressure transmitted from the powerchamber in the second passage to the regulator chamber on the basis of apredetermined characteristic.

Preferably, the master piston, control piston, pressure decrease valvedevice and pressure increase valve device are aligned along a commonaxis in the cylinder body, to define the regulator chamber between thepressure decrease valve device and the control piston.

BRIEF DESCRIPTION OF THE DRAWINGS

The above stated objects and following description will become readilyapparent with reference to the accompanying drawings, wherein likereference numerals denote like elements, and in which:

FIG. 1 is a sectional view of a hydraulic brake apparatus according toan embodiment of the present invention;

FIG. 2 is an enlarged sectional view of a master cylinder in thehydraulic brake apparatus of the above embodiment;

FIG. 3 is an enlarged sectional view of a regulator in the hydraulicbrake apparatus of the above embodiment;

FIG. 4 is an enlarged sectional view of a spool valve mechanism in thehydraulic brake apparatus of the above embodiment;

FIG. 5 is an enlarged sectional view of a poppet valve mechanism in thehydraulic brake apparatus of the above embodiment;

FIG. 6 is an enlarged sectional view of the spool valve mechanism inmotion according to the above embodiment;

FIG. 7 is an enlarged sectional view of the poppet valve mechanism inmotion according to the above embodiment;

FIG. 8 is a diagram showing a hydraulic brake pressure characteristicfor the hydraulic brake apparatus of the above embodiment;

FIG. 9 is a sectional view of a hydraulic brake apparatus according toanother embodiment of the present invention;

FIG. 10 is an enlarged sectional view of a master cylinder in thehydraulic brake apparatus of another embodiment of the presentinvention;

FIG. 11 is a sectional view of a hydraulic brake apparatus according toa further embodiment of the present invention;

FIG. 12 is an enlarged sectional view of a master cylinder in thehydraulic brake apparatus of the further embodiment of the presentinvention;

FIG. 13 is a diagram showing an embodiment of a pressure restrictiondevice according to the further embodiment of the present invention;

FIG. 14 is a diagram showing a characteristic of a relief valveaccording to the further embodiment of the present invention;

FIG. 15 is a diagram showing a hydraulic pressure characteristic of thefurther embodiment of the present invention;

FIG. 16 is a diagram showing another embodiment of the pressurerestriction device according to the further embodiment of the presentinvention;

FIG. 17 is a diagram showing a characteristic of a proportional pressuredecreasing mechanism according to the further embodiment of the presentinvention;

FIG. 18 is a diagram showing a hydraulic pressure characteristic ofanother embodiment of the pressure restriction device in the furtherembodiment of the present invention; and

FIG. 19 is a sectional view of a cut-off valve according to the furtherembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, there is illustrated a hydraulic brake apparatusfor a vehicle according to an embodiment of the present invention, whichincludes a cylinder body 1 provided with a master cylinder MC and aregulator RG. The master cylinder MC has a couple of pressure chambersR2, R4 to form a tandem-type master cylinder connected to a diagonalcircuit. A brake pedal 2 is disposed behind the cylinder body 1, i.e.,at the right side in FIG. 1, and served as the manually operated brakingmember according to the present invention. When a depressing force isapplied to the brake pedal 2 the force is transmitted as a braking forceto the master cylinder MC and the regulator RG through a push rod 3. Inresponse to the depressing force, a hydraulic brake pressure isgenerated from the two pressure chambers R2, R4, and applied to wheelbrake cylinders Wfr, Wrl which are operatively mounted on a front rightwheel FR and a rear left wheel RL, and wheel brake cylinders Wfl, Wrrwhich are operatively mounted on a front left wheel FL and a rear rightwheel RR, respectively. The regulator RG discharges regulated pressurein response to depression of the brake pedal 2, to assist movement ofthe master cylinder MC in response to operation of the regulator RG, asdescribed later.

In the cylinder body 1, there is formed a stepped bore which includesbores 1a, 1b, 1c having different inner diameters from one another, andin which master pistons 10, 20, and a control piston 30 are received todefine the pressure chamber R2 between the master pistons 10 and 20, anddefine the pressure chamber R4 between the master piston 20 and thecontrol piston 30. The rear end of the bore 1a is communicated with apower chamber R1 having an inner diameter larger than that of the bore1a. Opposite end portions of the control piston 30 are fluid-tightly andslidably received in the bore 1b of the smallest inner diameter and thebore 1a, respectively.

The master piston 10 has a land portion 11 formed around an outersurface of its front end portion, as shown in FIG. 2. The land portion11 retains an annular cup-like seal member 12 and an annular seal member13 to be fluid-tightly and slidably received in the bore 1a, with thefront end surface of the seal member 12 facing the rear end surface ofthe master cylinder 20. Therefore, the power chamber R1 and the pressurechamber R2 are separated by the seal members 12, 13. A main body 14 ofthe master piston 10 is supported by a cylindrical sleeve 15, the innersurface and outer surface of which are formed with annular grooves, andalso an annular groove on the inner surface which is axially remote fromthem by a certain distance. Annular seal members 16, 17 and an annularcup-like seal member 18 are received in those grooves to ensure asealing property against the power chamber R1. The front end portion ofthe master piston 10 is formed with a recess 10a which extends axiallyfrom its tip end surface, and a retainer 19 is mounted on it.

The master piston 20 has a land portion 21 formed around an outersurface of its rear end portion, and a land portion 22 of the same outerdiameter as that of the land portion 21, which is formed around an outersurface of its front end portion away from the land portion 21 by acertain distance. These land portions 21, 22 retain annular cup-likeseal members 23, 24 to be fluid-tightly and slidably received in thebore 1a. The opposite end portions of the master piston 20 are formedwith recesses 20a, 20b which extend axially from its tip end surfaces,and a radial recess 20c which is communicated with the recess 20athrough an axial passage 20d. Between the land portions 21 and 22, thereis defined an annular fluid chamber R3, which is communicated with areservoir 4 through a port 1e, and which can be communicated with thepressure chamber R2 through the recess 20c, passage 20d and recess 20a.And, a retainer 29 is mounted on the front end portion of the masterpiston 20.

A retainer 25 is mounted on a rear end portion of the master piston 20to prevent a valve member 26 from moving beyond the retainer 25 towardthe master piston 10. The tip end of the valve member 26 is covered by amember made of resilient material such as rubber, which can abut on anopening end of the passage 20d to shut off the same. At the other end ofthe valve member 26, a rod 27 is formed to be integral with the valvemember 26. And, the rod 27 is provided at its rear end with an engagingportion 28, which is slidably received in the recess 10a, and which canbe engaged with the retainer 19 to prevent the engaging portion 28 frommoving beyond the retainer 19 toward the master piston 20. A spring 5 ismounted between the retainer 19 of the master piston 10 and the retainer25 of the master piston 20 to urge them away from each other. The rearend position of the master piston 20 is set by an engaging pin 7 screwedinto the cylinder body 1.

As shown in FIG. 3, the control piston 30 has a relatively largediameter land portion 31 formed around an outer surface of its rear endportion, and a relatively small diameter land portion 32 formed aroundan outer surface of a portion axially away from the land portion 31 by acertain distance. The land portion 31 retains an annular cup-like sealmember 33, and the land portion 32 retains a seal member 34, so that theland portion 31 is fluid-tightly and slidably received in the bore 1a,while the land portion 32 is fluid-tightly and slidably received in thebore 1b. Therefore, the pressure chamber R4 and the fluid chamber R5 areseparated by the seal members 33, while the fluid chamber R5 and aregulator chamber R6, which will be described later, are separated bythe seal member 34. That is, the fluid chamber R5 is defined between theseal members 33 and 34, and communicated with the reservoir 4 through aport it. The opposite end portions of the control piston 30 are formedwith a recess 30a and a stepped recess 30b which extend axially from itstip end surfaces, and a radial passage 30c which is communicated withthe recess 30a through a passage 30d. A retainer 35 is mounted on a rearend portion of the control piston 30, and it can be engaged with thevalve member 36 as constructed in the same manner as the valve member 26to prevent the valve member 36 from moving beyond the retainer 35 towardthe master piston 10. At the other end of the valve member 36, a rod 37is formed to be integral with the valve member 36. And, the rod 37 isprovided at its rear end with an engaging portion 38, which is slidablyreceived in the recess 20b, and which can be engaged with the retainer29 to prevent the engaging portion 38 from moving beyond the retainer 29toward the control piston 30. A spool 53 which will be described lateris held at its rear end portion within the stepped recess 30b at thebottom portion thereof. A spring 6 is mounted between the retainer 29 ofthe master piston 20 and the retainer 35 of the control piston 30 tourge them away from each other.

Referring back to FIG. 1, ahead of the cylinder body 1, the regulator RGis formed, and connected to an auxiliary pressure source 40 fordischarging the power pressure. The regulator RG is adapted to regulatethe power pressure to produce a regulated pressure to be supplied to apressure control valve device, or a modulator PC as indicated by atwo-dotted chain line in FIG. 1. The modulator PC includeselectromagnetic valves, i.e., solenoid valves connected to a controller(not shown), and is adapted to control the regulated pressure suppliedto the wheel brake cylinders Wfr and etc. in accordance with drivingconditions of the vehicle. The auxiliary pressure source 40 includes ahydraulic pressure pump 42 and an accumulator 43. The pump 42 is drivenby an electric motor 41 to pressurize brake fluid in the reservoir 4 todischarge the pressurized brake fluid, or power pressure through a port1p into the regulator RG.

As shown in FIG. 3, the regulator RG includes a cylindrical sleeve 51which is received in the stepped bore 1c communicating with the bore 1b.The sleeve 51 has a plurality of circumferential grooves formed aroundits periphery, and annular seal members are fitted into the grooves,respectively. Radial passages 51e, 51f are formed between theneighboring seal members to communicate the hollow portion of the sleeve51 with a port 1s and a first passage P1, respectively. A regulatorchamber R6 is defined between the rear end surface of the sleeve 51 andthe front end surface of the control piston 30, and communicated withthe power chamber R1 as shown in FIGS. 1 and 2 through the passage P2.The hollow portion of the sleeve 51 is formed into a stepped bore havingbores 51a, 51b, 51c, 51d. The inside of the bore 51b of the smallestdiameter forms a drain chamber R7 which is communicated with thereservoir 4 through the passage 51e and port 1s. Received in the bore51a is a sleeve 52 in which a stepped bore 52a is formed and a radialpassage 52b is formed perpendicularly to the stepped bore 52a tocommunicate with the regulator chamber R6. A spool 53 is slidablyreceived in the stepped bore 52a of the sleeve 52. A plunger 54 isreceived in the bore 51b with its base end portion 54a slidably receivedin the bore 51b, and with the rear end surface of the portion 54aarranged in abutment with the tip end surface of the spool 53 of thespool valve mechanism 50.

A resilient member 70, which is formed into a columnar shape by rubberfor example, is disposed in the bore 51c. The plunger 54 extends throughthe resilient member 70 with its tip end placed within a poppet valvemechanism 60. An annular transmitting member 71 is disposed between thebase end portion 54a of plunger 54 and the resilient member 70, which isformed with a recess on a surface opposite to the surface in abutmentwith the transmitting member 71. A plate 72 is disposed in abutment withthe front end surface of the resilient member 70 to apply the hydraulicpressure equally to the whole surface of the resilient member 70. Withinthe bore 51c, a power output chamber R8 is defined between the resilientmember 70 and the poppet valve mechanism 60. The power output chamber R8is communicated with the passage P1 through the passage 51f of thesleeve 51. As shown in FIG. 1, the passage P1 is communicated with thepower chamber R1, which is communicated with the regulator chamber R6through a second passage P2. In other words, a space for regulating thehydraulic pressure is formed by the power output chamber R8, passage P1,power chamber R1, passage P2 and regulator chamber R6.

Next will be described the spool valve mechanism 50, which serves as thepressure decrease valve means according to the present invention. Asshown in FIG. 4, the mechanism 50 includes a spool 53 which is formedinto a stepped columnar shape with a plurality of labyrinth groovesformed on its large diameter portion. In the middle portion of the spool53 is mounted a retainer 56, which is accommodated in the stepped recess30b to be supported by the control piston 30. A spring 55 is mountedbetween the retainer 56 and the control piston 30 to urge the spool 53to contact with the bottom surface of the stepped recess 30b. At aportion of the sleeve 52 into which the spool 53 is fitted, the passage52b is always communicated with the regulator chamber R6, and adapted tobe communicated with the drain chamber R7 at the initial position of thespool 53. It is so arranged that area of space between the sleeve 52 andthe spool 53 is restricted by the large diameter portion of the spool 53in accordance with the forward movement of the spool 53, and finally thepassage 52b is closed. As shown in FIG. 3, the drain chamber R7 iscommunicated with the reservoir 4 (in FIG. 1) through the passage 51e ofthe sleeve 51 and the port is of the cylinder body 1. Therefore, whenthe spool 53 is placed in its initial position, the regulator chamber R6is communicated with the reservoir 4 to be filled with the brake fluidunder atmospheric pressure. As for the pressure decrease valve means,any devices other than the spool valve mechanism 50 may be employed.And, they may not necessarily be placed within the regulator RG, but maybe placed near the power chamber R1, for example.

As shown in FIG. 5, the poppet valve mechanism 60, which serves as thepressure increase valve means according to the present invention,includes a sleeve 61 which is formed into a cylinder with a bottom. Thesleeve 61 has a longitudinal hollow portion 61a defined therein, aradial passage 61b defined to be communicated therewith, and a passage61c defined in parallel with the passage 61a to penetrate the sleeve 61.At the center of the bottom of sleeve 61, an axial passage 61d isdefined to form a valve seat 61e opening to the hollow portion 61a. Onthe outer peripheral surface of the sleeve 61, a plurality of annulargrooves are formed to receive therein annular seal members. Between theneighboring seal members, there is defined a radial passage 61b, throughwhich the hollow portion 61a is communicated with a port 1p as shown inFIGS. 1 and 3. In the hollow portion 61a of the sleeve 61, are disposeda valve member 63, retainer 64, spring 65 and filter 66. By fitting asmall diameter portion of stepped columnar sleeve 62 into the hollowportion 61a, a power input chamber R9 is defined in the hollow portion61a of the sleeve 61. The power input chamber R9 can be communicatedwith the power output chamber R8 (in FIG. 3) through the passage 61d.The sleeve 62 has an axial passage 62a defined therein, and a radialpassage 62b defined perpendicularly to the passage 62a. The valve member63 has a valve portion 63a at its tip end, followed by a collar portion63b and a stepped columnar body having a large diameter portion 63c,intermediate diameter portion 63d and small diameter portion 63e. Theintermediate diameter portion 63d is slidably received in the axialpassage 62a, of the sleeve 62. The opening area of the axial passage62a, is set to be substantially the same as the area of the valveportion 63a to be seated on the valve seat 61e. The valve member 63 isreceived in the hollow portion 61a of the sleeve 61 together with thefilter 66. A spring 65 is mounted between the retainer 64 and the collarportion 63b of the valve member 63 to urge the valve portion 63a to beseated on the valve seat 61e. The small diameter portion of the sleeve62 is fitted into the hollow portion 61a of the sleeve 61 so as tosupport the intermediate portion 63d of the valve member 63 in the axialpassage 62a. As a result, a space 62c is formed between the front endsurface of the sleeve 61 and the rear end surface of the sleeve 62, sothat the axial passage 62a is communicated with power output chamber R8,i.e., a space facing the tip end of the valve portion 63a to be seatedon the valve seat 61e, through the passage 62b, space 62c and passage61c of the sleeve 61. Therefore, substantially the same pressure isapplied to the opposite ends of the valve member 63 in the axialdirection thereof, so that a load applied to the valve member 63 will bevery small. Furthermore, a plunger 54 is arranged to face the valveportion 63a of the valve member 63, with a small space formed betweenthe valve portion 63a and the tip end of the plunger 54 in its initialposition as shown in FIG. 5.

In the initial position as shown in FIGS. 1 and 3, therefore, theregulator chamber R6 is communicated with the reservoir 4 through thepassages 52a, 52b of the sleeve 52, the passage 51e of the sleeve 51 andthe port is, so that the inside of the regulator chamber R6 is underatmospheric pressure. When the control piston 30 is moved forward tomove the spool 53 forward, the passage 52b of the sleeve 52 is closed bythe outer surface of the spool 53 as shown in FIG. 6, and in turn, thevalve member 63 of the poppet valve mechanism 60 is opened as shown inFIG. 7. Consequently, the power pressure is supplied from the auxiliarypressure source 40 to the power chamber R1 through the passage P1, thenfed to the regulator chamber R6 through the passage P2 to increase thepressure in each chamber. When a force applied to the front land portion32 of the control piston 30 by the regulated pressure exceeds a forceapplied to the rear land portion 31 by the master cylinder pressure, thecontrol piston 30 is moved rearward to close the valve member 63 of thepoppet valve mechanism 60 and open the spool 53 of the spool valvemechanism 50, the pressure in the regulator chamber R6 (and powerchamber R1, power output chamber R8 and passages P1, P2) is reduced.With the above-described operation repeatedly performed, the pressure inthe chamber is regulated to provide the predetermined regulatedpressure.

Next will be explained overall operation of the hydraulic brake pressureapparatus as constituted above. FIGS. 1-3 show a state of the apparatusin the case where the brake pedal 2 is not depressed. If the brake pedal2 is depressed to push the master piston 10 forward (leftward in FIG. 1)through the push rod 3, the valve member 26 abuts on the master piston20 to close the passage 20d by the resilient member of the valve member26, so that the communication between the pressure chamber R2 and thefluid chamber R3 is cut off to provide a closed state. At the same time,the valve member 36 abuts on the control piston 30 to close the passage30d by the resilient member of the valve member 36, so that thecommunication between the pressure chamber R4 and the fluid chamber R5is cut off to provide a closed state. Provided that the communicationbetween the a pressure chamber R2 and the fluid chamber R3 is cut off,and that the communication between the pressure chamber R4 and the fluidchamber R5 is cut off, if the master piston 10 is moved in response todepression of the brake pedal 2, the master pistons 10, 20 and thecontrol piston 30 are held as shown in FIGS. 2 and 3, with the masterpistons 10 and 20 connected by the spring 5, and with the master piston20 and control piston 30 connected by the spring 6, so that they movetogether in a body. As a result, the passage 52b is closed by the spool53, which is supported in the control piston 30, to cut off thecommunication with the reservoir 4. At the same time, the power pressureis supplied from the auxiliary pressure source 40 to the power chamberR1 through the passage P1. Then, the master pistons 10, 20 move forwardto compress further the pressure chambers R2, R4, and discharge thehydraulic brake pressure, i.e., master cylinder pressure from ports 1x,1y. In this case, since a sealing diameter of the land portion 31 of thecontrol piston 30 is larger than the sealing diameter of the landportion 32, the hydraulic brake pressure of a value greater than themaster cylinder pressure, i.e., regulated pressure is generated inaccordance with the movement of the control piston 30. Therefore, themaster piston 10 is assisted to move forward by the power pressure,which is supplied from the power output chamber R8 into the powerchamber R1 through the passage P1 in response to depression of the brakepedal 2, i.e., the regulated pressure.

During the operation as described above, when the force applied to thecontrol piston 30 by the regulated pressure in the regulator chamber R6exceeds the force applied to the control piston 30 by the mastercylinder pressure in the pressure chambers R2, R4, the control piston 30is moved in such a direction as to open the spool 53 of the spool valvemechanism 50 and close the valve member 63 of the poppet valve mechanism60, so that the pressure in the regulator chamber R6 is reduced. Whenthe relationship between the forces applied to the control piston 30 isreversed, the control piston 30 is moved in such a direction as to closethe spool 53 of the spool valve mechanism 50 and open the valve member63 of the poppet valve mechanism 60, so that the pressure in theregulator chamber R6 is increased. With the above-described movement ofthe control piston 30 and the opening or closing operation of the spoolvalve mechanism 50 and the poppet valve mechanism 60 in response to themovement of the control piston 30 repeatedly performed, the regulatedpressure in the chamber is regulated to be greater than the mastercylinder pressure by a predetermined value.

In practice, it is so controlled that the force applied to the controlpiston 30 by the regulated pressure applied to the area of the smalldiameter land portion 32 for receiving the pressure, and the forceapplied to the control piston 30 by the master cylinder pressure appliedto the area of the large diameter land portion 31 for receiving thepressure will be equal. Accordingly, the regulated pressure, which isgreater than the master cylinder pressure by the predetermined value andsubstantially proportional to the master cylinder pressure, isdischarged to provide a first brake pressure characteristic between thebrake pedal input and the master cylinder pressure. In the normalbraking operation, the hydraulic brake pressure in the power outputchamber R8 is transmitted to the resilient member 70 to deform the same,so that the resilient member 70 abuts on the transmitting member 71 topress the valve member 63 to be seated on the valve seat 61e, and pressthe spool 53 to increase the opening area of the passage 52b.Accordingly, the regulated pressure is reduced to provide a second brakepressure characteristic, which has a smaller increasing rate than thatof the first brake pressure characteristic, i.e., gentle increasinggradient, between the brake pedal input and the master cylinderpressure.

According to the present embodiment, therefore, the boosting operationis performed appropriately with a proper characteristic as indicated bya solid line in FIG. 8, even in case of the rapid depression of thebrake pedal 2. Consequently, the desired braking characteristic combinedwith the first brake pressure characteristic and second brake pressurecharacteristic (right side of a bent in FIG. 8) will be obtained. Asindicated by a broken line in FIG. 8, the brake pressure characteristicaccording to the prior art is unstable in case of the rapid depressionof the brake pedal 2. In the case where the modulator PC is provided,the regulated pressure is controlled in response to the drivingconditions of the vehicle to supply the pressure into the wheel brakecylinders, so as to perform a desired control. Furthermore, the brakefluid fed from the pressure passage P1 to the power chamber R1 isreturned to the regulator chamber R6 through the passage P2, accordingto the present embodiment. Therefore, it is easy to fulfill the brakefluid in the whole brake system with no air remained in the powerchamber R1.

FIGS. 9 and 10 show another embodiment of the present invention, whereina check valve 80, which serves as the one way valve means according tothe present invention, is disposed in the passage P1 at a portionthereof connected to the power chamber R1. The check valve 80 includes acylindrical case 81 with a bottom on which a valve seat 82 is formed, aball valve 83 which is accommodated in the case 81, and a spring 84which urges the ball valve 83 to be seated on the valve seat 82. Insteadof the check valve 80, any valves may be used for the one way valvemeans. The modulator PC is connected to the passage P1 between the poweroutput chamber R8 and the check valve 80. At the downstream of the checkvalve 80, a pressure sensor (not shown) is provided for use incontrolling the hydraulic pressure by the modulator PC. The remainingstructure of the present embodiment is substantially the same as theembodiment as described before, so that its explanation will be omitted.

According to the hydraulic pressure control apparatus of the embodimentas shown in FIGS. 9 and 10, the regulated pressure is controlled by themodulator PC in accordance with the vehicle conditions, and fed into thewheel brake cylinders Wfr and etc. to perform a desired pressurecontrol. For example, when the hydraulic brake pressure control such asthe anti-skid control is performed, the solenoid valves (not shown) inthe modulator PC are controlled in accordance with the brakingconditions, so that the regulated pressure fed into the wheel brakecylinders Wfr and etc. is controlled to prevent the wheel FR and etc.from being locked. In this case, the brake fluid is allowed to be fedfrom the poppet valve mechanism 60 to the power chamber R1, and itsreverse flow is prevented. Therefore, even if the brake fluid iscompensated during the control by the modulator PC to provide suddenly apressure decreasing state, the pressure in the power chamber R1 will beheld by means of the check valve 80. Consequently, the variation ofpressure in the power chamber R1 can be reduced to obtain an appropriatefeeling in braking operation without causing the vibration of the brakepedal 2.

In the case where the pressure sensor (not shown) is disposed downstreamof the check valve 80 for monitoring the depressed condition of thebrake pedal 2 according to the embodiment as shown in FIGS. 9 and 10, anoutput signal of the pressure sensor will be of little noise, so thatthe control will be made accurately.

FIGS. 11 and 12 show a further embodiment of the present invention,wherein a relief valve 100, which serves as the pressure decreasingmeans according to the present invention, is disposed in the passage P2at a portion thereof connected to the power chamber R1, and a normallyopen two-port two-position electromagnetic valve (solenoid valve) 200,which serves as the valve means according to the present invention, isdisposed in a passage P3 which is connected to the passage P2 inparallel with the relief valve 100. Those relief valve 100 and solenoidvalve 200 serve as the pressure restriction means according to thepresent invention. The solenoid valve 200 is connected to an electroniccontrol unit ECU, and controlled thereby to be opened or closed inresponse to operation of the brake pedal 2. According to the presentembodiment, a stroke sensor 201 is provided for detecting a stroke ofthe brake pedal 2, and its output signal is fed into the electroniccontrol unit ECU, in which the depressing speed of the brake pedal 2 isdetected, as shown in FIG. 13 which illustrates those devices especiallyused for the present embodiment. Instead of the stroke sensor 201, apressure sensor (not shown), a depressing force sensor (not shown) fordetecting the depressing force of the brake pedal 2, or wheel speedsensors (not shown) may be employed. The remaining structure of thepresent embodiment is substantially the same as the embodiment asdescribed in FIGS. 1-7, so that its explanation will be omitted.

According to the hydraulic pressure control apparatus of the embodimentas shown in FIGS. 11 and 12, the solenoid valve 200 is normally placedin its open position to communicate the power chamber R1 with theregulator chamber R6 through the passage P3. When the electronic controlunit ECU determines that the depressing speed of the brake pedal 2 hasexceeded a predetermined value, the solenoid valve 200 is placed in itsclosed position to shut off the passage P3. Consequently, the powerchamber R1 is communicated with the regulator chamber R6 only throughthe relief valve 100 having a characteristic as indicated by a solidline in FIG. 14. As a result, the hydraulic pressure in the regulatorchamber R6 increases in accordance with a linear relationship with thehydraulic pressure in the power chamber R1, with a predeterminedpressure Pd delayed comparing with a characteristic as indicated by aone-dotted chain line in FIG. 14. Therefore, a hydraulic pressurecharacteristic as indicated by a broken line in FIG. 15 can be obtained.That is, a first brake pressure characteristic K1 is provided inaccordance with pressure receiving area of the control piston 30 in theregulator chamber R6, and a second brake pressure characteristic K2 isprovided by the resilient member 70 to obtain a desired servocharacteristic.

When the brake pedal 2 is depressed rapidly, and the operating speed ofthe brake pedal 2, which is detected on the basis of the output signalof the stroke sensor 201, is determined by the control unit ECU to haveexceeded a predetermined value, the solenoid valve 200 is placed in itsclosed position, to cut off the communication between the power chamberR1 and the regulator chamber R6. Thus, according to the presentembodiment, the stroke sensor 201 and the control unit ECU serve as therapid operation detecting means of the present invention. After thesolenoid valve 200 was placed in its closed position, the power pressurefed into the power chamber R1 from the auxiliary pressure source 40through the passage P1 is transmitted to the regulator chamber R6through the relief valve 100. Consequently, the hydraulic pressurecharacteristic indicates a steep gradient K3 of building-up transient asindicated by a broken line in FIG. 15 until the relief valve 100 wasopened, and the hydraulic pressure in the regulator chamber R6 is heldto be relatively low after the relief valve 100 is opened, so that itindicates a relatively gentle gradient K4, and finally it indicates thesecond gradient K2. The gradient K4 can be set on the basis of theproperty of the relief valve 100.

Under the braking condition as described above, when the depressingforce applied to the brake pedal 2 is released, the braking force isreduced proportionally, while it is held to be of the predeterminedvalue when the solenoid valve 200 is placed in its closed position. Whenthe brake pedal 2 is released, it is determined by the control unit ECUthat the brake pedal 2 has been released, on the basis of the outputsignal of the stroke sensor 201. As a result, the solenoid valve 200 isplaced in its original open position, so that the braking force will bereleased immediately.

FIG. 16 shows another embodiment of the pressure restriction meansaccording to the present invention, wherein a proportional pressuredecreasing mechanism 202 is disposed in parallel with the solenoid valve200. As the proportional pressure decreasing mechanism 202, is used aknown proportioning valve (not shown) which has a characteristic asindicated by a solid line in FIG. 17, wherein the hydraulic pressure inthe regulator chamber R6 increases in accordance with a linearrelationship with the hydraulic pressure in the power chamber R1,varying at a more gentle gradient than that of an ordinarycharacteristic as indicated by a one-dotted chain line in FIG. 17. Inthe normal braking operation, therefore, the first brake pressurecharacteristic K1 and second brake pressure characteristic K2 areprovided as indicated by a solid line in FIG. 18. When the brake pedal 2is depressed rapidly, and the speed of depression of the brake pedal 2is determined by the control unit ECU to exceed the predetermined value,the solenoid valve 200 is placed in its closed position, the powerchamber R1 and the regulator chamber R6 can be communicated with eachother only through the proportional pressure decreasing mechanism 202.In this case, the hydraulic pressure characteristic indicates a gradientK5, which is more gentle than that of the characteristic K3 as shown inFIG. 15, but steeper than that of the normal braking characteristic, andindicates the second gradient K2 thereafter, as indicated by a brokenline in FIG. 18.

As for the valve means in the pressure restriction means of the presentinvention, a cut-off valve 90 as shown in FIG. 19 may be employedinstead of the solenoid valve 200. The cut-off valve 90 includes apressure receiving portion 91a communicated with the power chamber R1, avalve member 91 formed with an orifice 91b, a valve seat 92 communicatedwith the regulator chamber R6, and a spring 93 for biasing the valvemember 91 away from the valve seat 92. Therefore, normally, the powerchamber R1 is communicated with the regulator chamber R6 through theorifice 91b of the valve member 91 and the valve seat 92. Once the powerpressure is discharged from the poppet valve mechanism 60 to increasethe hydraulic pressure in the power output chamber R8 rapidly, apressure difference will be caused by the orifice 91b between the powerchamber R1 and the regulator chamber R6. Accordingly, the valve member91 will be forced to be seated on the valve seat 92 against the biasingforce of the spring 93, so that the communication between the powerchamber R1 and the regulator chamber R6 will be cut off. In the casewhere the cut-off valve 90 is used, however, it is necessary to combineit with the proportioning pressure decreasing mechanism 202 which candecrease the pressure in a returning step of the valve 90.

It should be apparent to one skilled in the art that the above-describedembodiments are merely illustrative of but a few of the many possiblespecific embodiments of the present invention. Numerous and variousother arrangements can be readily devised by those skilled in the artwithout departing from the spirit and scope of the invention as definedin the following claims.

What is claimed is:
 1. A hydraulic brake apparatus for applying brakingforce to each wheel of a vehicle in response to depression of a manuallyoperated braking member comprising:a cylinder body mounted on saidvehicle; a reservoir for storing brake fluid; a master cylinder having amaster piston slidably received in said cylinder body to define apressure chamber ahead of said master piston and a power chamber behindsaid master piston, the brake fluid in said reservoir being fed intosaid pressure chamber, and said master piston being moved in response tooperation of said manually operated braking member to dischargehydraulic brake pressure from said pressure chamber; an auxiliarypressure source for pressurizing the brake fluid in said reservoir todischarge power pressure of a predetermined value; a control pistonslidably disposed in said cylinder body ahead of said master piston tobe movable in response to movement of said master piston, said controlpiston defining ahead thereof a regulator chamber, and exposing a rearend thereof to said pressure chamber; a first passage for communicatingsaid auxiliary pressure source with said power chamber; a second passagefor communicating said power chamber with said reservoir through saidregulator chamber; pressure increase valve means disposed in said firstpassage for opening or closing said first passage in response tomovement of said control piston; and pressure decrease valve meansdisposed in said second passage for opening or closing said secondpassage in response to movement of said control piston.
 2. A hydraulicbrake apparatus as set forth in claim 1, wherein said master piston,control piston, pressure decrease valve means and pressure increasevalve means are aligned along a common axis in said cylinder body,disposing said pressure decrease valve means between said regulatorchamber and said reservoir, and defining said regulator chamber betweensaid control piston and said pressure decrease valve means.
 3. Ahydraulic brake apparatus as set forth in claim 1, further comprisingone way valve means for allowing the brake fluid to flow from saidpressure increase valve means to said power chamber and preventing thereverse flow.
 4. A hydraulic brake apparatus as set forth in claim 3,further comprising a modulator connected with one end of said one wayvalve means to be connected with said pressure increase valve means,said modulator being adapted to supply the hydraulic brake pressuredischarged from said pressure increase valve means into wheel brakecylinders of said vehicle in accordance with the driving conditions ofsaid vehicle.
 5. A hydraulic brake apparatus as set forth in claim 3,wherein said one way valve means is a check valve disposed in said firstpassage at a portion thereof opening to said power chamber.
 6. Ahydraulic brake apparatus as set forth in claim 3, wherein said masterpiston, control piston, pressure decrease valve means and pressureincrease valve means are aligned along a common axis in said cylinderbody, defining said regulator chamber between said control piston andsaid pressure decrease valve means, said power chamber beingcommunicated with said reservoir through said regulator chamber whensaid pressure decrease valve means opens said second passage.
 7. Ahydraulic brake apparatus as set forth in claim 1, further comprisingpressure restriction means for restricting the hydraulic brake pressurefed from said power chamber into said regulator chamber in response tooperation of said manually operated braking member.
 8. A hydraulic brakeapparatus as set forth in claim 7, wherein said pressure restrictionmeans comprises:valve means disposed in said second passage for normallyopening said second passage, and closing said second passage when saidmanually operated braking member is operated rapidly; and pressuredecreasing means disposed in parallel with said valve means fordecreasing the hydraulic brake pressure fed from said power chamber intosaid regulator chamber in accordance with a predeterminedcharacteristic.
 9. A hydraulic brake apparatus as set forth in claim 8,wherein said valve means comprises:rapid operation detecting means fordetecting operation of said manually operated braking member to output acut-off signal when said manually operated braking member is operated ata speed greater than a predetermined speed; and a normally openelectromagnetic valve for closing said second passage when said rapidoperation detecting means outputs the cut-off signal.
 10. A hydraulicbrake apparatus as set forth in claim 8, wherein said valve meansincludes a cut-off valve comprising a valve seat formed between saidpower chamber and said regulator chamber, a valve member with one endthereof exposed to said power chamber and with the other end thereofseated on said valve seat, and a spring for urging said valve memberaway from said valve seat, said valve member being formed with anorifice for communicating said power chamber with said regulatorchamber.
 11. A hydraulic brake apparatus as set forth in claim 8,wherein said pressure decreasing means includes a relief valve forcommunicating therethrough when the hydraulic brake pressure fed fromsaid power chamber into said regulator chamber exceeds a predeterminedpressure.
 12. A hydraulic brake apparatus as set forth in claim 8,wherein said pressure decreasing means includes a proportional pressuredecreasing mechanism for decreasing the hydraulic brake pressuredischarged therefrom substantially in proportion to the hydraulic brakepressure fed thereinto.
 13. A hydraulic brake apparatus as set forth inclaim 7, wherein said master piston, control piston, pressure decreasevalve means and pressure increase valve means are aligned along a commonaxis in said cylinder body, defining said regulator chamber between saidcontrol piston and said pressure decrease valve means, to communicatesaid power chamber with said regulator chamber and said pressureincrease valve means, and wherein said pressure restriction means isdisposed in said second passage.
 14. A hydraulic brake apparatus as setforth in claim 13, wherein said pressure restriction meanscomprises:valve means disposed in said second passage for normallyopening said second passage, and closing said second passage when saidmanually operated braking member is operated rapidly; and pressuredecreasing means disposed in parallel with said valve means fordecreasing the hydraulic brake pressure fed from said power chamber intosaid regulator chamber in accordance with a predeterminedcharacteristic.
 15. A hydraulic brake apparatus as set forth in claim 1,further comprising pressure control means disposed between said powerchamber and said regulator chamber in said second passage forcontrolling the pressure transmitted from said power chamber to saidregulator chamber on the basis of a predetermined characteristic.